This project investigates the immune response, particularly the kinds of lymphocytes involved in making antibody. We have established that both thymus-derived and bone-marrow-derived cells are involved. We will investigate the activities of these cells in the thymus, the marrow and the peripheral lymphoid tissue. We will look at the turnover of cells, their response to antigens and nonspecific cell mitogens. There appears to be a differential effect of corticosteroids on thymus-derived and marrow-derived cells, depending on their state of maturation and location. This will be investigated using measurements of antibody production and cell-mediated immunity. Species differences in the response of lymphoid cells will be studied. The induction of tolerance to haptens on various carriers will be looked at.